An elevator installation comprises an elevator car and usually a counterweight, which are movable in an elevator shaft or along free-standing guide devices. For producing the movement the elevator installation has at least one drive with at least one respective drive wheel, which carries the elevator car and the counterweight by way of one or more belts and/or transmits the required drive forces to these. A drive wheel can in that case be formed in a manner known per se as a drive pulley or equally as a wheel with a smaller diameter, particularly also as a drive output shaft of the drive itself.
The elevator car and the counterweight can be supported and driven by way of the same at least one supporting and drive belt, which is guided over the at least one drive wheel. Alternatively, the elevator car and the counterweight can also be coupled together by way of at least one support belt running over a deflecting roller, so that the counterweight rises when the elevator car is lowered and conversely, wherein the drive of the elevator car and the counterweight takes place by a drive unit via at least one separate drive belt. Whereas in drive belts tension forces are transmitted to drive belts by drive wheels in order to move the elevator car or the counterweight, pure support belts are deflected not over drive wheels, but merely over deflecting elements, particularly rotatable or fixed deflecting rollers, and accept the weight force of the elevator car or the counterweight. In most elevator installations the supporting function and driving function are fulfilled by the same at least one supporting and drive belt.
An elevator belt according to the present invention can be used for each of the above-described functions, thus equally as a supporting belt, as a drive belt or as a supporting and drive belt, as one of several belts arranged in parallel or as an individual belt.
Where no distinction is required between drive wheels and deflecting rollers, these are generally termed belt wheels in the following.
An elevator belt with a belt body of polyurethane is known from European patent EP 1 060 305 B1, in which a tensile carrier arrangement with cables of multiply stranded wires for transmission of a tension force in longitudinal direction of the elevator belt is arranged.
When the tensile carriers during production of this elevator belt are embedded in the belt body, the individual tensile carriers can displace relative to one another. An unfavorable arrangement of the tensile carriers in a transverse direction of the belt can thereby arise. For example, two tensile carriers can lie closely adjacent in the belt body or even contact one another. Since the tensile carriers when looping around a belt pulley, particularly a drive wheel, exert, due to the tension forces transmitted by them, impart substantial pressure stresses on the belt body the risk exists that the belt body is damaged by the increased local loading which occurs with closely adjacent, particularly mutually contacting, tensile carriers. In the extreme case tensile carriers lying closely together can cut through the belt body.
If, as in EP 1 060 305 B1, the elevator belt is contoured, the risk additionally exists that tensile carriers during production are positioned in regions of the belt body with smaller wall thickness, which less satisfactorily accept the pressure and shear forces exerted by the tensile carriers and can deflect and thus are exposed to an increased risk of damage.